Tropical Storm LESLIE

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TROPICAL STORM LESLIE DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122012
500 PM AST FRI AUG 31 2012
THE STORM LOOKS A LITTLE BETTER ORGANIZED ON VISIBLE IMAGERY THIS
AFTERNOON WITH AN INCREASE IN CONVECTION IN ADDITION TO MICROWAVE
OVERPASSES SHOWING THE CENTER BECOMING MORE EMBEDDED IN THE
OVERCAST. INTENSITY ESTIMATES...HOWEVER...ARE UNCHANGED...SO THE
INITIAL WIND SPEED IS KEPT AT 55 KT. WHILE THE VERTICAL SHEAR IS
EXPECTED TO REMAIN LIGHT-TO-MODERATE IN THE SHORT TERM...MOST OF
THE GLOBAL MODELS ARE NOW SHOWING AN INCREASINGLY HOSTILE
ENVIRONMENT AFTER THAT TIME. THESE CONDITIONS ARE DUE TO AN
UPPER-LEVEL HIGH MOVING WEST OF THE CENTER...CAUSING AN INCREASE IN
NORTHWESTERLY SHEAR. MOST OF THE INTENSITY GUIDANCE NOW SHOW
LESLIE ONLY AS A CATEGORY ONE HURRICANE IN A FEW DAYS TIME. THE
OFFICIAL FORECAST IS REDUCED SLIGHTLY FROM THE PREVIOUS ONE...IN
BEST AGREEMENT WITH A BLEND OF THE INTENSITY CONSENSUS AND THE LGEM
MODEL. THERE IS SOME CHANCE OF LESLIE FINDING A MORE FAVORABLE
ENVIRONMENT IN THE LONG TERM...BUT ITS LIKELY SLOW MOTION AT THAT
TIME COULD CAUSE UPWELLING UNDER THE STORM...SO THE NHC FORECAST
WILL STAY CONSERVATIVE.
A SERIES OF MICROWAVE PASSES GIVES A GOOD INITIAL MOTION ESTIMATE OF
295/16. THERE HAS BEEN A SUBTLE WESTWARD SHIFT IN MOST OF THE
RELIABLE MODEL GUIDANCE DURING THE FORECAST PERIOD...PERHAPS
INITIALLY DUE TO THE RIDGE BETWEEN KIRK AND LESLIE BEING A BIT
STRONGER THAN EXPECTED. THE GLOBAL MODELS ARE CONSISTENT IN
FORECASTING A BREAK IN THE SUBTROPICAL RIDGE IN A FEW DAYS
TIME...WHICH SHOULD CAUSE LESLIE TO TURN NORTHWESTWARD AND
NORTHWARD IN 3 TO 4 DAYS. BY THE END OF THE FORECAST...LITTLE
MOTION IS EXPECTED AS THE CYCLONE IS CAUGHT IN LIGHT STEERING
CURRENTS TO THE SOUTHEAST OF BERMUDA. THE OFFICIAL NHC PREDICTION
IS SHIFTED WESTWARD TO COME CLOSER TO THE DYNAMICAL MODEL
CONSENSUS... ALTHOUGH THE MODEL CONSENSUS IS STILL A BIT WEST OF
THE NEW FORECAST.
FORECAST POSITIONS AND MAX WINDS
INIT 31/2100Z 16.7N 51.0W 55 KT 65 MPH
12H 01/0600Z 17.7N 53.2W 60 KT 70 MPH
24H 01/1800Z 18.9N 55.9W 60 KT 70 MPH
36H 02/0600Z 20.1N 58.1W 65 KT 75 MPH
48H 02/1800Z 21.5N 60.0W 70 KT 80 MPH
72H 03/1800Z 24.1N 62.0W 70 KT 80 MPH
96H 04/1800Z 26.0N 62.5W 70 KT 80 MPH
120H 05/1800Z 27.0N 63.0W 75 KT 85 MPH
$$
FORECASTER BLAKE
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